In the manufacture and repair of the typical bearing assemblies for a shaft and housing through which high axial loads are imposed and radial forces are encountered, the cumulative tolerance attributable to manufacture of the various components has posed problems.
Particularly under circumstances when the bearing assembly operates in a hostile environment, such as the environment encountered when drilling bore holes in the earth, such as in well drilling, mining, pipeline installation, or the like, the cumulative manufacturing tolerance, as well as unequal wear of the parts has been a problem.
For example, in the drilling of bore holes in the earth using an in-hole fluid motor to drive a drill bit, the drill bit is attached to the shaft which is driven by the fluid motor. The shaft is hollow to allow the circulation of the drilling fluid through the motor to drive the shaft and through the shaft to the bit to flush cuttings from the bore holes and cool the bit. Whether the drilling fluid is gas, air, or liquid mud, the fluid contains very erosive particles which can cause bearing wear when the fluid flows through the bearings to also cool the bearings. In any event, the effective penetration of the drill bit through the earth formation is dependent upon the application of axial loading or weight on the bit cutters, the load or weight being transmitted to the drive shaft through the bearings from the housing. In such bearing assemblies, it is customary to employ spring elements to provide a spring cushion and absorb shock during operation of the drill.
When the bearings do not or cannot collectively transmit the load, and only certain bearings transmit all of the load excessive wear and ultimate destruction of the overloaded bearings may result. If the springs, due to tolerance, do not carry a proportionate share of the load, the overloaded springs may be destroyed resulting in excessive shock loading of the bearings. Such an event can cause cessation of the drilling operation and retrieval of the drilling apparatus for bearing repair, long before the drill bit may require change, and the drilling operation is thus terminated in an uneconomic period of time in the hole.